The development of mobile communication networks and the growth of Wireless Local Area Network-based services are driving forces behind the increase in the number of users that communicate wirelessly by using mobile stations, which are also referred to as “mobile nodes.” Mobile Internet Protocol (IP) has been developed to facilitate mobility management, in particular by managing the locations of the mobile nodes and by providing communication for the mobile nodes during handover from one wireless network to another. Mobile IP advantageously allows a mobile node to transmit and receive data seamlessly while maintaining the same IP address. There are various versions of Mobile IP protocol, including Mobile IPv4 (MIPv4), MIPv6, and Proxy Mobile IPv6 (PMIPv6).
FIG. 1 depicts a schematic diagram of telecommunications system 100 in the prior art. System 100 comprises mobile node 101; correspondent node 102; foreign networks 103-1 through 103-N, wherein N is a positive integer; local mobility anchor (LMA) 104; mobile access gateway (MAG) 105; home network 106; and Internet network 107. The elements are interconnected as shown.
Mobile node 101 is a device that is capable of handling a telephone call, or another type of media transmission, on behalf of its user. Typically, node 101 is either a mobile device or portable device such as a cellular phone, a wireless handset, a laptop computer with or without a resident softphone, or another type of telecommunications appliance that is capable of exchanging media signals such as voice, video, and so forth. Node 101 is able to call, or be called by, another node within telecommunications system 100 such as correspondent node 102. Node 102 is another telecommunications device that is capable of exchange media signals. For example, node 101 is able to dial a telephone number that routes to node 102 and to then exchange media signals with node 102. Both mobile node 101 and corresponding node 102 are endpoints that must be IPv6-capable, but the endpoints themselves do not have to be capable of supporting mobility-related signaling protocols such as MIPv6.
Foreign network 103-n, wherein n has a value between 1 and N, inclusive, provides the connectivity between visiting mobile nodes that are attached to one or more gateways within the network, such as mobile node 101, or between an attached mobile node and a correspondent node or nodes in another network, such as correspondent node 102. The communications signals transported within network 103-n convey bitstreams of encoded media, such as audio, video, and so forth. Network 103-n comprises an Internet Protocol-based (IP-based) network for the purpose of transporting the media signals. Network 103-n comprises one or more interconnected data-processing systems such as switches, servers, routers, and gateways. These data-processing systems, and therefore network 103-n, operate in accordance with Proxy Mobile Internet Protocol, version 6 (i.e., PMIPv6).
Two of the types of data-processing systems that operate in accordance with PMIPv6 within system 100 are local mobility anchor 104 and mobile access gateway 105, the mobility access gateway that serves network 103-1 being depicted.
Local mobility anchor (LMA) 104 serves as the home agent for mobile node 101 in the proxy mobile IPv6 domain. It is the topological anchor point for node 101's home network prefix, and manages the node 101's binding state. As such, LMA 104 acts as the entry point for all traffic packets destined for mobile node 101. The presence of LMA 104 is necessary because when node 101 moves out of its home address network (i.e., network 106), mobile node 101's home address cannot be used for direct communication by another node. This is because the home address is an invalid Internet Protocol address in the visited network (i.e., network 103-1 in the case of node 101). LMA 104 receives the traffic packets with the home address of node 101 as the destination address, and then forwards those packets to the mobile access gateway with which mobile node 101 is currently attached (i.e., MAG 105).
Mobile access gateway (MAG) 105 manages the mobility-related signaling for mobile nodes (e.g., node 101) attached to the gateway's access link. MAG 105 is responsible for tracking the mobile node's movement on the access link and for signaling the mobile node's local mobility anchor (e.g., LMA 104) on behalf of the mobile node. In addition, MAG 105 establishes a “tunnel” with the local mobility anchor, in order to enable the mobile node to use an address from its home network prefix, and then emulates the mobile node's home network.
For example, when mobile node 101 first enters PMIP network 103-1 and registers, and after determining that node 101 is eligible for service, MAG 105 transmits a proxy binding update (PBU) to LMA 104, in order to inform the LMA of the new location of node 101. LMA 104 transmits a binding acknowledgment (BA) message with node 101's home-network prefix, creates a Binding Cache Entry (BCE), and sets up a bi-directional tunnel entry point. MAG 105 transmits a remote access (RA) message to node 101, in order to simulate the node's home network. Whenever LMA 104 detects packets addressed to node 101's home address, such as from correspondent node 102, the local mobility anchor intercepts those packets, encapsulates those packets, and sends them to node 101's proxy, which is at the “care-of” address assigned by MAG 105 to node 101. MAG 105 de-encapsulates each packet received and routes the packet to node 101. In handling packets originating from mobile node 101, MAG 105 acts as a default router in that all of the traffic sent from node 101 to the destination node (correspondent node 102) has to be routed through it. MAG 105 encapsulates the packets received from node 101 and transmits them to LMA 104. LMA 104 then de-encapsulates the tunneled packets and routes them to correspondent node 102.
PMIPv6 provides an improvement over previously standardized mobility management protocols such as MIPv6 and MIPv4. However, since PMIPv6 focuses only on the Internet Protocol layer, it does not take into consideration the impact of handover on the higher protocol layer applications such as real-time communications based on Session Initiation Protocol (SIP). In PMIPv6, all of the traffic is tunneled through a bi-directional tunnel when a mobile node changes its point of attachment. Although this tunneling is adequate for some non-real-time traffic such as email, the tunneling can add overhead and delay to the packets, thereby affecting quality of service and making communication that involves real-time traffic problematic.
What is needed is a technique for transmitting packets in a Proxy Mobile Internet Protocol-based network, without some of the disadvantages in the prior art.